JPH08143667A - Polyimide composition - Google Patents

Abstract

PURPOSE: To efficiently obtain a polyimide composition used for an oriented liquid crystal membrane, etc., by conducting the dehydrating ring closure of a polyamide having acid groups obtained from a specific diamino compound and a tetracarboxylic acid dianhydride, with a polyamide having acid groups containing a specific diaminobenzoic acid ester. CONSTITUTION: This polyimide composition is obtained by blending a polyamide having acid groups prepared by reacting a diamino compound expressed by formula I (A is a divalent organic group) [provided, not containing the structural unit of formula II (R<1> is a 1-20C alkyl or an alkoxy; (m) is an integer of 1-20; (n) is an integer of 1-2)] (e.g. 1,3-phenylenediamine) with a tetracarboxylic acid dianhydride expressed by formula III (B is a tetra valent organic group) (e.g. 3,3',4,4'-biphenyltetracarboxylic acid dianhydride) in a solvent (e.g. N-methyl-2- pyrrolidone), with a polyamic acid consisting of 3,5-diaminobenzoic acid ester derivative of the formula II and a tetracarboxylic acid dianhydride of the formula III and conducting the dehydrating ring closure of the mixture to obtain a resin composition consisting of the structural units expressed by formulas IV and V and containing 5-95mol% structural unit of the formula IV.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyimide composition having a side chain.

[0002]

2. Description of the Related Art Polyimide resin has the highest heat resistance among commercially available plastics, is excellent in impact resistance, dimensional stability, electrical characteristics and abrasion resistance, and is an excellent plastic with little change in characteristics due to temperature. . Utilizing these characteristics, it is used as a material for aerospace and machinery as well as electrical and electronic fields such as insulating materials, sealing materials and printed circuit boards. Further, in recent years, attention has been paid as a material for an alignment film of a liquid crystal display element, and many polyimide-based alignment films have been developed.

In a liquid crystal display element used in a clock or a calculator, a twisted nematic (hereinafter abbreviated as TN) having a structure in which the arrangement direction of nematic liquid crystal molecules is twisted 90 degrees between a pair of upper and lower electrode substrates. ) Mode is mainly adopted. Also, a super twisted nematic (hereinafter abbreviated as STN) in which the twist angle of the liquid crystal is 180 to 270 degrees.
Modes are also now commonplace, and are being produced in large quantities for large displays such as word processors and personal computers. The alignment film used in such a liquid crystal display device is not enough to simply align the liquid crystal molecules, and in order to improve the responsiveness and ensure the bistability, the alignment film is not provided between the substrate surface and the liquid crystal molecules. A pretilt angle of 1 to 4 degrees in the TN mode and 4 to 8 degrees in the STN mode must be provided. Further, in recent years, a super-twist birefringence effect (hereinafter abbreviated as SBE) mode has been developed as a display element having more excellent contrast and viewing angle dependency. In this method, a high pretilt angle of 20 to 30 degrees is required. .

Further, although it is desired to color the liquid crystal display element, there is a color filter method as one of the color display methods which are widely used at present, and its use for liquid crystal color televisions and personal computer displays is expanding. . This method is a method in which a color filter is provided between the substrate and the transparent electrode. In this method, a polyimide film is prepared by applying a polyamic acid to a substrate provided with a transparent electrode and a color filter, followed by drying and firing, but since the dye-type color filter is relatively inferior in heat resistance, the filter is fired. There is a possibility of fading and deterioration. Therefore, when attaching a color filter, it is preferable to bake at a temperature as low as possible.

Japanese Unexamined Patent Publication (Kokai) No. 4-100020 discloses a diamino compound having a linear alkyl ester in a side chain,
A polyimide alignment film having a structural unit of the above formula [1], which is composed of 3 ', 4,4'-biphenyltetracarboxylic dianhydride, and a liquid crystal display device using the same are disclosed. However, there is no specific description about the pretilt angle of this alignment film. On the other hand, JP-A-3-179322,
JP-A-3-179323 and JP-A-5-272
Japanese Patent Laid-Open No. 44-44 discloses a polyimide-based liquid crystal alignment film containing a diamine having a liquid crystal group in a side chain as a monomer.
However, these polyimides are manufactured at 200 to 250 ° C.
It requires firing for 1 to 2 hours, and when a dye color filter with low heat resistance is attached, the
There is a risk that the deterioration of the color may occur.

The present inventor has a spacer having a flexible alkyl chain at the side chain and a diamine having a liquid crystal group such as a phenylcyclohexyl group or a phenylbicyclohexyl group at the tip thereof, and 2,2-bis (4 -Aminophenoxyphenyl) -propane was used as a monomer and was invented as a polyimide excellent in low-temperature curability, and a patent application was filed in Japanese Patent Application No. 6-173269.
When this polyimide was used as a liquid crystal alignment film, the pretilt angle was a relatively low value of about 8 degrees. Therefore, as a result of further studies, the reaction between a diamine component having a liquid crystal group such as a phenylcyclohexyl group or a phenylbicyclohexyl group and a tetracarboxylic dianhydride via a spacer composed of a flexible alkyl chain on the side chain. When the obtained polyimide alignment film having the structural unit of the above formula [2] was produced, it was discovered that it had a high pretilt angle of 30 degrees or more, and a patent application was filed in Japanese Patent Application No. 6-234162. However, since this polymer is a homopolymer, it was difficult to freely control the pretilt angle according to the purpose.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, that is, in the production of polyimide, for electrical and electronic materials which can be produced by firing at a lower temperature and a shorter time, particularly liquid crystals. Provided is a polyimide composition which is excellent in liquid crystal alignment property without causing fading of a color filter or the like during cell production and is useful as a liquid crystal alignment film capable of freely controlling a pretilt angle in a wide range of 5 to 30 degrees. That is.

[0008]

Therefore, as a result of intensive studies, the present inventors have found that any polyimide resin represented by the structural unit of the above formula [1] and a phenylcyclohexyl group or a phenylbicyclohexyl group in the side chain. Like,
A diamine component having a liquid crystal group is obtained as a monomer,
A composition of a polyimide resin composed of the structural unit of the above formula [2], particularly a polyimide resin composed of the structural unit of the above formula [6], which is obtained by using a diamine component having a flexible alkyl chain in a side chain as a monomer, Since the composition of the polyimide resin composed of the structural unit [2] can be produced by firing at a relatively low temperature for a short time, it does not cause discoloration of the color filter during production of the liquid crystal cell,
The film-forming property, the adhesion to the glass substrate and the thermal stability were excellent, and the liquid crystal orientation was also good. Further, the structural unit of the formula [1] or the structural unit of the formula [6] and the formula [2]
The present invention was completed by finding that the pretilt angle can be freely controlled in a wide range of 5 to 30 degrees by changing the molar ratio with the structural unit of.

That is, the constitution of the present invention is as follows. (1) A structural unit represented by the formula [1] and a structural unit represented by the formula [2] (however, the structural unit of the formula [1] is not included), and the structural unit of the formula [1] is 5 A polyimide composition which is 95 mol%.

[Chemical 10] (A represents a divalent organic group and B represents a tetravalent organic group.)

[Chemical 11] (M is an integer of 1 to 20, n is an integer of 1 to 2, R ¹ is an alkyl group or an alkoxy group having 1 to 20 carbon atoms, and B is a tetravalent organic group.) (2) Formula [3] A polyamino acid obtained by reacting a diamino compound represented by the formula (however, not containing the structural unit of the formula [5]) with a tetracarboxylic dianhydride represented by the formula [4] in a solvent; The polyamino acid obtained by reacting the diamino compound represented by the formula (4) with the tetracarboxylic acid dianhydride represented by the formula [4] in a solvent was mixed so that the polyamic acid accounts for 5 to 95 mol% of the whole. A polyimide composition obtained by dehydration and ring closure by post-heating.

[Chemical 12] (A represents a divalent organic group.)

[Chemical 13] (B represents a tetravalent organic group.)

Embedded image (M is an integer of 1 to 20, n is an integer of 1 to 2 and R ¹ is an alkyl group or an alkoxy group having 1 to 20 carbon atoms.) (3) A structural unit represented by the formula [6] and a formula [6]. 7] and the structural unit of the formula [6] is 5 to
The polyimide composition according to claim 1, which is 95 mol%.

[Chemical 15] (R ² represents an alkyl group having 1 to 20 carbon atoms.)

Embedded image (M is an integer of 1 to 20, n is an integer of 1 to 2 and R ¹ is an alkyl group or an alkoxy group having 1 to 20 carbon atoms.) (4) A diamino compound represented by the formula [8] and a formula

A polyamic acid obtained by reacting a tetracarboxylic dianhydride represented by [9] in a solvent, a diamino compound represented by the formula [5], and a formula

A polyimide composition obtained by subjecting a tetracarboxylic acid dianhydride represented by [9] and a polyamic acid obtained by reacting in a solvent to mixing, followed by dehydration and ring closure by heating.

[Chemical 17] (R ² represents an alkyl group having 1 to 20 carbon atoms.)

Embedded image (5) A liquid crystal alignment film comprising the polyimide composition according to any one of items (1) to (4). (6) A liquid crystal display device comprising the liquid crystal alignment film according to claim 5.

To produce the polyimide composition of the present invention, two polyamic acids obtained by the condensation reaction of diamine and tetracarboxylic dianhydride are mixed in a solution state and then coated on a substrate, A method of forming a polyimide composition on a substrate by heat treatment and dehydration reaction is preferable.

A detailed description will be given below. A diamino compound represented by the formula [3] or a 3,5-amino group represented by the formula [8]
Diaminobenzoic acid alkyl ester and tetracarboxylic dianhydride represented by the formula [4], or the formula

A single polyamic acid is produced by condensation with 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) represented by [9].

The 3,5-diaminobenzoic acid alkyl ester represented by the above formula [8] can be produced according to Chemical formula 19.
That is, in the presence of triethylamine, alcohol and 3,
Condensed with 5-dinitrobenzoyl chloride to give 3,5-
Dinitrobenzoic acid alkyl ester is obtained, and this compound is catalytically reduced in the presence of a palladium-carbon catalyst to produce 3,5-diaminobenzoic acid alkyl ester.

[0013]

[Chemical 19] (R ² represents an alkyl group having 1 to 20 carbon atoms.)

Formula [5] (m is an integer of 1 to 20, n is 1 to
An integer of 2 and R ¹ represents an alkyl group or an alkoxy group having 1 to 20 carbon atoms. ) 3,5-diaminobenzoic acid [4- (trans-4-alkyl-cyclohexyl) phenoxyalkyl] ester represented by the formula (4) and a tetracarboxylic acid dianhydride represented by the formula [4] or BPDA A type of polyamic acid is produced.

The 3,5-diaminobenzoic acid [4- (trans-4-alkyl-cyclohexyl) phenoxyalkyl] ester represented by the above formula [5] can be produced according to Chemical Formula 20. That is, first, 4- (trans-4-alkyl-cyclohexyl) phenol and α, ω-alkylenehalohydrin were added to dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (in the presence of excess potassium carbonate). It is condensed in a solvent such as NMP) or dimethylformamide (DMF) at 100 to 150 ° C. to obtain an alcohol compound. Subsequently, this compound was condensed with 3,5-dinitrobenzoyl chloride in the presence of triethylamine,
3,5-Dinitrobenzoic acid [4- (trans-4-alkyl-cyclohexyl) phenoxyalkyl] ester is obtained. Finally, this compound is catalytically reduced in the presence of a palladium-carbon catalyst to produce 3,5-diaminobenzoic acid [4- (trans-4-alkyl-cyclohexyl) phenoxyalkyl] ester.

[0016]

Embedded image (M represents an integer of 1 to 20, n represents an integer of 1 to 2, R ¹ represents an alkyl group or an alkoxy group having 1 to 20 carbon atoms, and X represents halogen.)

The condensation reaction between the above diamine and tetracarboxylic dianhydride is carried out under anhydrous conditions under the conditions of DMAc, NMP and D.
It is carried out in a solvent such as MF, dimethyl sulfoxide (DMSO), sulfolane, butyrolactone, cresol, phenol, halogenated phenol, cyclohexanone, dioxane or tetrahydrofuran, preferably NMP solvent at a temperature of -10 to 30 ° C.

After mixing the above two kinds of polyamic acid in a solution state, the mixture is baked at about 200 ° C. to obtain a polyimide composition.

The molar ratio of each structural unit represented by the formula [1] and the formula [2] in the polyimide composition is represented by the formula [1].
Is preferably 5 to 95 mol%, and the formula [2] is preferably 95 to 5 mol%. The ratio of formula [1] or formula [2] is 5 mol%
The effects of blending are lost in the following cases. This relationship is similarly established in a polyimide composition composed of a blend of structural units represented by formulas [6] and [7].

The m in the structural units represented by the formulas [2] and [7] in the polyimide molecule is preferably 3 or more, more preferably 6 or more. When m is 3 or less, flexibility in the side chain direction is reduced, and therefore, high temperature firing is required during production.

The length of the alkyl group in the structural unit represented by the formula [6] in the polyimide molecule is preferably 3 or more, more preferably 6 or more. If it is 3 or less, the flexibility in the side chain direction is lowered, so that the low temperature curability is deteriorated.

The substrate used for the liquid crystal alignment film and the liquid crystal display device is usually a glass substrate, and electrodes (specifically, ITO (indium oxide-tin oxide) or tin oxide transparent electrodes are formed on the substrate. Furthermore, between this electrode and the substrate, an insulating film for preventing alkali elution from the substrate,
An undercoat film such as a color filter or a color filter overcoat may be provided, and an insulating film on the electrode,
An overcoat film such as a color filter film may be provided. Further, a TFT (Thin-Film-Transistor) element, an MIM (Metal Insulator Metal Meta) are provided on the electrodes.
An active element such as an l-Insulator-Metal element may be formed. For these electrodes, undercoat, and other internal structure of the liquid crystal cell, the structure of a conventional liquid crystal display element can be used.

In order to form the polyimide composition or the liquid crystal alignment film of the present invention on the substrate, the above-mentioned two polyamic acids are mixed in a desired ratio, and NMP, DMAc, DMF, D are added.
It is dissolved in a solvent such as MSO, butyl cellosolve, ethyl carbitol and adjusted to a 0.1 to 30% by weight solution, and this solution is applied by a brush coating method, a dipping method, a spin coating method, a spray method,
It is applied on a substrate by a printing method or the like, baked at 100 to 450 ° C., preferably 180 to 220 ° C., and dehydrated and cyclized to form a polyimide composition film. If the surface of the substrate is treated with a silane coupling agent before coating and a film of the polyimide composition is formed thereon, the adhesion between the film and the substrate can be improved. Then, the coated surface is rubbed in one direction with a cloth or the like to obtain a liquid crystal alignment film.

A cell is formed using a substrate for a liquid crystal display element, liquid crystal is injected, and the injection port is sealed to form a liquid crystal display element. As the liquid crystal to be enclosed, various liquid crystals such as a normal nematic liquid crystal and a liquid crystal added with a dichroic dye can be used. The liquid crystal alignment film of the present invention has good liquid crystal alignment,
By selecting the structure and mixing ratio of the polyamic acid,
The pretilt angle can be freely controlled in a wide range of 30 degrees.

The liquid crystal display device of the present invention is provided with a liquid crystal alignment film having a good liquid crystal alignment property and capable of freely controlling the pretilt angle in a wide range of 5 to 30 degrees, that is, the liquid crystal alignment film according to the present invention. The feature is that it is usually a substrate,
It is composed of a voltage applying means, a liquid crystal alignment film, a liquid crystal layer and the like.

[0026]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Next, the physical properties of the polyimide composition and the liquid crystal alignment film obtained in the examples were measured by the following methods. Decomposition temperature (Td): A differential thermogravimetric simultaneous measurement device (TG / DTA-220 manufactured by Seiko Denshi Kogyo Co., Ltd.) was used to measure the temperature at a temperature rising rate of 10 ° C./min. Pretilt angle: Measured using a magnetic field capacitance method.

[0028]

【Example】

Example 1 Production of a polyimide composition comprising structural units represented by the formulas [1] and [2] (A is 1,3-phenylene group, B is 3,
3 ′, 4,4′-biphenylene group is shown): 1) Preparation of polyimide precursor consisting of structural unit represented by the formula [1]: In a 50 ml three-necked flask, 0.6061 g of 1,3-phenylenediamine ( 1.50 mmol),
NMP (3.0 ml) was added, and the mixture was dissolved with stirring under a nitrogen stream at room temperature. Next, this solution was kept at 10 ° C., and BPDA was added at 0.44.
13 g (1.50 mmol) was added. The BPDA on the vessel wall was washed off with 3 ml of NMP and the reaction was carried out for 3 hours. The obtained varnish was directly used in the next step.

2) 3,5-Diaminobenzoic acid [4- (trans-4-ethyl-cyclohexyl) phenoxypropyl] ester represented by the formula [5] (m = 3, n = 1,
Production of R ¹ = C ₂ H ₅ ). In a 1 L three-necked flask equipped with a condenser and a stirrer, 500 ml of dimethylformamide and 20.4 g (0.10 g) of 4- (trans-4-ethyl-cyclohexyl) phenol.
mol) and 41.4 g (0.30 mol) of potassium carbonate were added and stirred at room temperature. 18.1 g (0.13 mol) of 3-bromo-1-propanol was added thereto, and the mixture was vigorously stirred at 100 ° C. After reacting for 10 hours, this solution was added to 2 L of water and extracted with 1.5 L of ethyl acetate. Then, the organic layer was washed 3 times with 3N hydrochloric acid and 3 times with 2N aqueous sodium hydroxide solution.
Further washed with water. The obtained ethyl acetate layer was dried over anhydrous sodium sulfate, the solvent was distilled off under reduced pressure, and the obtained crystal was recrystallized twice with n-heptane to give 4- (trans-
17.6 g (0.067 mol) of 4-ethyl-cyclohexyl) phenoxypropanol was obtained. Melting point is 68.5
It was ~ 69.9 ° C.

Subsequently, 300 ml of THF was placed in a 500 ml three-necked flask equipped with a stirrer, and 18.0 g (0.068 mol) of 4- (trans-4-ethyl-cyclohexyl) phenoxypropanol and 11.4 ml of triethylamine were added thereto. The mixture was stirred at 0 ° C. 3,5 to this
-Dinitrobenzoyl chloride 15.7 g (0.068 m
ol) was dissolved in 50 ml of THF, and the solution was added dropwise over 30 minutes, and the reaction was performed for 6 hours. After completion of the reaction, this liquid was added to 1 L of water and extracted with 1.5 L of ethyl acetate. Subsequently, the organic layer was washed with 3N hydrochloric acid three times, saturated aqueous sodium hydrogen carbonate three times, and further washed with water. The obtained ethyl acetate layer was dried over anhydrous sodium sulfate, the solvent was distilled off under reduced pressure, and the obtained crystal was recrystallized twice with ethyl acetate to give 3,5-dinitrobenzoic acid [4- (trans- 4-ethyl-cyclohexyl)
Phenoxypropyl] ester 23.3 g (0.051 m
ol) was obtained. The melting point was 108.0-109.4 ° C. After confirming the structure of this compound by IR and NMR, the compound was subjected to catalytic reduction.

That is, 3,5-dinitrobenzoic acid [4
1- (trans-4-ethyl-cyclohexyl) phenoxypropyl] ester (15.0 g, 0.033 mol) was dissolved in 300 ml of ethyl acetate, and 1.50 g of 5% palladium-carbon was added and catalytic reduction was performed at room temperature and atmospheric pressure. After completion of the reaction, the catalyst was filtered off, the solvent was distilled off under reduced pressure, and the obtained crystals were recrystallized twice with n-heptane / ethyl acetate to give 3,
5-diaminobenzoic acid [4- (trans-4-ethyl-
Cyclohexyl) phenoxypropyl] ester 11.
1 g (0.028 mol) was obtained. The melting point of this compound was 91.5 to 92.4 ° C.

3) Preparation of polyamic acid comprising structural unit represented by the formula [2]: In a 50 ml three-necked flask, 3,
5-diaminobenzoic acid [4- (trans-4-ethyl-
Cyclohexyl) phenoxypropyl] ester 0.5
942 g (1.50 mmol) and 3.0 ml of NMP were added, and the mixture was dissolved with stirring under a nitrogen stream at room temperature. Then add this liquid to 1
Keep at 0 ℃, 0.4413g BPDA (1.50mmo
l) Added. The BPDA on the vessel wall was washed off with 3 ml of NMP and the reaction was carried out for 3 hours. The obtained varnish was directly used in the next step.

4) Preparation of polyimide composition: 0.50 g of the varnish produced in 1) and 1.00 g of the varnish produced in 3) were mixed and stirred until uniform. This mixture was mixed with NMP / butyl cellosolve = 1/1 solvent for 4.0 w
After diluting to t%, it was coated on a glass substrate with ITO by a spin coating method (spinner method). 200 coated substrates
It was baked at 30 ° C. for 30 minutes to obtain a substrate on which a film of a polyimide composition having a film thickness of 600 angstrom was formed. This polyimide composition had a decomposition temperature of 391.4 ° C. and had good adhesion to a glass substrate.

5) Preparation of Cell and Measurement of Pretilt Angle Rubbing treatment was applied to the film surfaces of the two substrates on which the polyimide composition was formed, and a liquid crystal cell with a cell thickness of 20 μm was assembled so that the rubbing directions were anti-parallel, and the chisso was prepared. Liquid crystal FB-01 manufactured by Co., Ltd. was enclosed. Then, the cell in which the liquid crystal was sealed was subjected to heat treatment at 120 ° C. for 30 minutes.
After the heat treatment, it was allowed to cool and the pretilt angle was calculated to be 16.7 degrees. Also, when observing this cell with a microscope,
It showed excellent liquid crystal alignment with no disorder in alignment.

Example 2 Production of Polyimide Composition Comprising Structural Units Represented by Formulas [6] and [7]: 1) 3,5-Diaminobenzoic Acid Stearyl Ester (R ² = Represented by Formula [8] C ₁₈ H ₃₇₎
Manufacturing of. To a 500 ml three-necked flask equipped with a stirrer, 200 ml of THF was placed, and 13.5 g (0.050 mol) of stearyl alcohol and triethylamine 8.
4 ml was added and stirred at 0 ° C. To this, 11.5 g (0.050 mol) of 3,5-dinitrobenzoyl chloride was added to T
The solution dissolved in 50 ml of HF was added dropwise over 30 minutes, and the reaction was performed for 6 hours as it was. After completion of the reaction, this liquid was added to 1 L of water and extracted with 1.5 L of ethyl acetate. Subsequently, the organic layer was washed with 3N hydrochloric acid three times, saturated aqueous sodium hydrogen carbonate three times, and further washed with water. The obtained ethyl acetate layer was dried over anhydrous sodium sulfate, the solvent was distilled off under reduced pressure, and the obtained crystal was recrystallized twice with ethyl acetate to give 3,5-dinitrobenzoic acid stearyl ester 18.1 g ( 0.039 mol) was obtained. The melting point was 75.9-76.7 ° C. The structure of this compound is
After confirmation by R and NMR, catalytic reduction of the compound was performed.

That is, 8.0 g (0.017 mol) of 3,5-dinitrobenzoic acid stearyl ester was dissolved in 300 ml of ethyl acetate to prepare 1.0 g of 5% palladium-carbon.
Was added to carry out catalytic reduction under normal temperature and pressure. After completion of the reaction, the catalyst was filtered off, the solvent was distilled off under reduced pressure, and the obtained crystals were recrystallized twice with n-heptane / ethyl acetate to give 4,5-diaminobenzoic acid stearyl ester 4.48 g (0 0.011m
ol) was obtained. The melting point of this compound is 81.8-82.6 ° C.
Met.

2) Preparation of polyimide precursor consisting of structural unit represented by the formula [6]: 3,5-diaminobenzoic acid stearyl ester in a 50 ml three-necked flask.
6061 g (1.50 mmol) and 3.0 ml of NMP were added and dissolved under stirring at room temperature under a nitrogen stream. Then add this liquid to 1
Keep at 0 ℃, 0.4413g BPDA (1.50mmo
l) Added. The BPDA on the vessel wall was washed off with 3 ml of NMP and the reaction was carried out for 3 hours. The obtained varnish was directly used in the next step.

3) Preparation of polyimide precursor consisting of structural unit represented by formula [7]: A polyimide precursor was prepared according to 3) of Example 1. The obtained varnish was directly used in the next step.

4) Preparation of polyimide composition: 0.11 g of the varnish prepared in 2) and 1.0 of the varnish prepared in 3).
0 g of the mixture was mixed and the same procedure as in 4) of Example 1 was performed. The decomposition temperature of this polyimide composition is shown in Table 1.

5) Preparation of Cell and Measurement of Pretilt Angle A cell was prepared according to 5) of Example 1. Table 1 shows the pretilt angles.

Examples 3 to 6 In 4) and 5) of Example 3 except that the component ratio of the polyimide precursor represented by the formula [6] and the polyimide precursor represented by the formula [7] is changed. It was done in compliance. Table 1 shows the component ratios and the physical properties of the obtained polyimide composition.

[0042]

[Table 1]

[0043]

The polyimide composition obtained according to the present invention can be produced by firing at low temperature for a short time and has a decomposition temperature of 3 or less.
It can be used at high temperature as high as 20 ° C or higher. Further, the liquid crystal alignment film using the present polyimide composition has excellent adhesion to a glass substrate and liquid crystal alignment. Furthermore, by changing the composition ratio, the pretilt angle can be freely controlled in a wide range of about 5 to 30 degrees, so TN, STN, S
It is useful as a material for an alignment film of a liquid crystal cell for BE.

[Brief description of drawings]

1] IR of the polyimide film obtained in Example 3
It is a spectrum figure.

Claims (6)

[Claims] 1. A structural unit represented by formula [1] and a structural unit represented by formula [2] (however, the structural unit of formula [1] is not included), wherein the structural unit of formula [1] is A polyimide composition which is 5 to 95 mol%. Embedded image (A represents a divalent organic group and B represents a tetravalent organic group.) (M is an integer of 1 to 20, n is an integer of 1 to 2, R ¹ is an alkyl group or an alkoxy group having 1 to 20 carbon atoms, and B is a tetravalent organic group.) 2. Obtained by reacting a diamino compound represented by the formula [3] (however, the structural unit of the formula [5] is not included) with a tetracarboxylic dianhydride represented by the formula [4] in a solvent. A polyamic acid obtained by reacting a diamino compound represented by the formula [5] with a tetracarboxylic acid dianhydride represented by the formula [4] in a solvent. A polyimide composition obtained by dehydration and ring closure by heating after mixing so as to be ˜95 mol%. Embedded image (A represents a divalent organic group.) (B represents a tetravalent organic group.) (M is an integer of 1 to 20, n is an integer of 1 to 2 and R ¹ is an alkyl group or an alkoxy group having 1 to 20 carbon atoms.) 3. The structural unit of the formula [6] and the structural unit of the formula [7], wherein the structural unit of the formula [6] accounts for 5 to 95 mol% of the whole. Polyimide composition. [Chemical 6] (R ² represents an alkyl group having 1 to 20 carbon atoms.) (M is an integer of 1 to 20, n is an integer of 1 to 2 and R ¹ is an alkyl group or an alkoxy group having 1 to 20 carbon atoms.) 4. A polyamic acid obtained by reacting a diamino compound represented by the formula [8] with a tetracarboxylic dianhydride represented by the formula [9] in a solvent, and a diamino represented by the formula [5]. A polyimide composition obtained by mixing a compound and a polyamic acid obtained by reacting a tetracarboxylic dianhydride represented by the formula [9] in a solvent, followed by dehydration and ring closure by heating. Embedded image (R ² represents an alkyl group having 1 to 20 carbon atoms.) 5. A liquid crystal alignment film comprising the polyimide composition according to any one of claims 1 to 4. 6. A liquid crystal display device comprising the liquid crystal alignment film according to claim 5.